The invention relates to a method and apparatus for information transfer between two or more stations, which are all connected to each other for serial data transfer by means of a write line and a read line separated from the write line. The write line, after passing through all the stations, is connected to the read line at the end. A time frame structure is formed by periodic synchronizing information stored at the beginning of the write line. The frame structure comprises various data words which each form a data channel at the same position in successive frame.
Such a method is, for example, Known from the German Patent Application DE-OS 34 27 981. Each occupied data channel represents a connection from one station to another, that is to say information is only transferred from the one station to the other each time.
However, two stations are often connected to each other such that they exchange information, specifically, the second station simultaneously transfers information back to the first station. This is usually effected through a second data channel. Consequently, for simultaneous mutual information exchange between two stations also two data channels are required, so that with a limited number of data channels the number of stations, that are able to simultaneously transfer information, is limited too.
It is an object of the invention to provide a method of the type mentioned in the preamble, that utilizes the individual data channels more effectively and therefore enables more connections between stations.